1. Field of the Invention
The present invention relates to propelling and braking apparatuses for a zero pressure accumulator and, more particularly, to an accumulator conveyor in which the supporting rollers are normally in intimate contact with the propelling force and when the propelling force is removed therefrom by inflating an expansible tube disposed between the propelling and braking apparatus, a braking force is applied to a plurality of the article supporting rollers.
2. Description of the Relevant Art
The use of an expansible tube device in combination with a pressurized pneumatic apparatus for controlling the propulsion of articles along a conveyor system is disclosed in U.S. Pat. No. 3,770,102 issued to DeGood on Nov. 6, 1973. The patent to DeGood discloses an accumulator conveyor having a powered propelling member passing through a plurality of independent operating zones arranged in tandem along the conveyor. In each zone the propelling member is shiftable between an article propelling and an article non-propelling position by pneumatically actuated pressure rollers acting on a propelling member. A valve operated by an article detecting sensor in each zone, operates a supply or exhausts fluid pressure to the actuators. An auxiliary valve system connected between the secondary pressure source and the actuators operates to shift all of the operating zones into an article propelling position, thereby overriding the accumulative function of the conveyor.
In U.S. Pat. No. 3,724,642 issued to DeGood on Apr. 3, 1973, there is disclosed a powered roller accumulator similar to the one discussed above. In addition, the patent also discloses a braking device which engages the powered rollers in order to stop the rotation when the propelling member is shifted to a non-driving position, thereby preventing movement of articles along the conveyor.
In U.S. Pat. No. 4,278,166 there is disclosed an apparatus which includes drive wheels which have a peripheral drive surface adapted for driving engagement with at least one carrier roller. An annular groove is found in the drive surface of each drive wheel and receives a drive cable therein, with the wheels formed to increase frictional gripping between the drive wheels and the carrier rollers. The drive wheels are each pivotally moved into and out of engagement with the carrier rollers by an independent fluid pressure activator. A braking mechanism mechanically coupled to the drive wheel mounting bracket applies braking forces to each roller contacted by the drive roller by pivotal movement.
However, all of the disclosed systems apply a braking apparatus to a singular roller in each tandem section of the conveyor. If additional rollers are to be afforded braking pressure, the mechanism must be duplicated at various positions in each section. Thus, the braking device as disclosed is unable to be applied to a plurality of article carrying rollers simultaneously. An article moving on the conveyor will not be stopped until it reaches the braking roller, and thus, an article traveling behind the first article will come into contact therewith, and apply pressure thereto in order to be stopped. It can be readily seen that the braking roller would be required to be spaced a distance apart that is less than the dimension of the article being propelled along the conveyor, in order to reduce the amount of pressure between articles that are stopped. The cost and inconvenience of providing a large quantity of braking rollers is readily overcome with the use of the instant invention.
In U.S. Pat. No. 3,323,636 issued to Gotham on June 6, 1967, there is disclosed a power driven roller conveyor which is driven from below by a moving belt urged into contact with the article supporting rollers by spring-actuated pulleys which limit the frictional driving force on the several driven rollers. The rollers require continual adjustment in order to insure the proper amount of frictional contact between the moving belt and the supporting rollers, since the spring tension varies with time and temperature. A braking apparatus for stopping the moving articles on the conveyor is not disclosed therein.
In U.S. Pat. No. 3,232,415 issued to Gotham on Feb. 1, 1966, there is disclosed a power driven roller system with an apparatus to allow and compensate for accumulation of articles being conveyed while the conveyor is in operation. The disclosed apparatus utilizes a bearingless roller accumulation conveyor which includes a sloped bracket mechanism disposed beneath the rollers and encompassing the drive belt. The rollers are permitted to move in a horizontal direction by the driving belt and may be urged in the opposite horizontal direction when packages traveling on the supporting rollers start to accumulate providing forces in the opposite horizontal direction. By moving a supporting roller in the opposite or reverse direction, the supporting roller moves rearwardly up the ramp of the U-shaped bracket and out of contact with the drive belt, thereby stopping further accumulation of the packages on the conveyor.
In U.S. Pat. No. 4,273,239 issued to J. A. Thwaites et al on June 16, 1981, a zero pressure accumulator conveyor is disclosed which includes a combination propelling and braking apparatus that applies braking forces to a plurality of supporting rollers in a first or normal position and is moved to a second or driving position wherein a drive belt is placed in intimate frictional contact with the supporting rollers while removing the braking forces. The apparatus disclosed therein utilizes an expansible tube disposed between the driving belt mechanism and the braking mechanism and is shiftable from the first or normal braking position to the second or driving position by permitting pressurized fluid to enter the expansible tube. The system is maintained in the stopped or normal (first) position with the braking forces applied when there is no pressurized fluid in the expansible tube.